On 10/15/2012 12:53 PM, Tony Lindgren wrote:
> * Paul Walmsley <paul@xxxxxxxxx> [121014 22:26]:
>>
>> After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix
>> saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
>> started crashing during boot with omap2plus_defconfig:
>>
>> [ 3.875122] mmcblk0: mmc0:e624 SD04G 3.69 GiB
>> [ 3.915954] mmcblk0: p1
>> [ 4.086639] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
>> [ 4.093719] Modules linked in:
>> [ 4.096954] CPU: 0 Not tainted (3.6.0-02232-g759e00b #570)
>> [ 4.103149] PC is at vfp_reload_hw+0x1c/0x44
>> [ 4.107666] LR is at __und_usr_fault_32+0x0/0x8
>>
>> It turns out that the context save/restore fix unmasked a latent bug
>> in commit 5aaf254409f8d58229107b59507a8235b715a960 ("ARM: 6203/1: Make
>> VFPv3 usable on ARMv6"). When CONFIG_VFPv3 is set, but the kernel is
>> booted on a pre-VFPv3 core, the code attempts to save and restore the
>> d16-d31 VFP registers. These are only present on non-D16 VFPv3+, so
>> this results in an undefined instruction exception. The code didn't
>> crash before commit 846a136 because the save and restore code was
>> only touching d0-d15, present on all VFP.
>>
>> Fix by implementing a request from Russell King to add a new HWCAP
>> flag that affirmatively indicates the presence of the d16-d31
>> registers:
>>
>> http://marc.info/?l=linux-arm-kernel&m=135013547905283&w=2
>>
>> and some feedback from Måns to clarify the name of the HWCAP flag.
>>
>> Signed-off-by: Paul Walmsley <paul@xxxxxxxxx>
>> Cc: Tony Lindgren <tony@xxxxxxxxxxx>
>> Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
>> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
>> Cc: Dave Martin <dave.martin@xxxxxxxxxx>
>> Cc: Måns Rullgård <mans.rullgard@xxxxxxxxxx>
>
> This fixes the error above on my 2430sdp:
>
> Tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
Fixes same error on 2420 H4.
Tested-by: Jon Hunter <jon-hunter@xxxxxx>
Cheers
Jon
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